Add venetianblind interface

And fix a bug in shutter, which should extend closable
instead of simpleclosable just like blinds and awnings.

libnymea/interfaces/interfaces.qrc

@@ -76,5 +76,6 @@
         <file>powerswitch.json</file>
         <file>barcodescanner.json</file>
         <file>irrigation.json</file>
+        <file>venetianblind.json</file>
     </qresource>
 </RCC>

libnymea/interfaces/shutter.json

@@ -1,3 +1,3 @@
 {
-    "extends": "simpleclosable"
+    "extends": "closable"
 }

libnymea/interfaces/venetianblind.json

@@ -0,0 +1,13 @@
+{
+    "extends": "extendedblind",
+    "description": "Venetian blinds that can be tilted. Venetian blinds must support an angle and specify the minimum and maximum supported angle. For instance, if a venetian blinds supports tilting from horizontal to vertical by 90°, the minValue should be set to 0° and the maxValue to 90°. For venetian blinds that support tilting both direction, that is, a total of 180°, the minValue should be -90° and the maxValue should be 90°. 0° is always the horizontal position.",
+    "states": [
+        {
+            "name": "angle",
+            "type": "double",
+            "unit": "UnitDegree",
+            "minValue": "any",
+            "maxValue": "any"
+        }
+    ]
+}